The invention relates to a process for the preparation of carboxylic acid esters via oxidative esterification.
The production of methyl methacrylate (MMA) from methacrolein (MAL), methanol, and oxygen is known. For example, U.S. Pat. No. 4,518,796 discloses the use of a Pd-bismuth (Bi) catalyst. However, that catalyst did not give high MMA selectivity, which is desired for this reaction.
U.S. Pat. No. 5,892,102 discloses MAL oxidative esterification catalysts that include Pd—Bi—X intermetallics, where X can be a variety of elements, on a ZnO or CaCO3 support. These supports are undesirable from a mechanical stability, likely acid resistance, and long-term catalyst life standpoint.
In view of the deficiencies of the prior art, it would be desirable to have an improved oxidative esterification catalyst for selectively producing MMA.